The invention relates to a rotary anode X-ray tube with at least one sliding bearing, which is filled with a liquid lubricant. Such an X-ray tube is known, inter alia, from European Laid Open Patent Application 141,476. The sliding bearings for the bearing of the rotary anode are in this case formed by so-called spiral flute bearings, which have a narrow gap and a pattern of flutes on one of their bearing surfaces. In the bearing gap, which is bounded on the one side by a smooth bearing surface and on the other side by the surface with the flute pattern, there is the lubricant. The flutes are formed in such a way that the lubricant remains in the bearing during the operation of the rotary anode X-ray tube with a predetermined direction of rotation. Adjoining the spiral flute bearing is a surface which is prepared in such a way that it cannot be wetted by the lubricant, for example by a titanium-oxide or silicon-oxide carbide layer.
In the case of such rotary anode X-ray tubes, it may happen, in particular during transit, that drops of lubricant escape from the bearing and get into the part of the vacuum space of the X-ray tube which is exposed to a strong electric field in operation of the tube. These drops of lubricant impair the high-voltage strength of the X-ray tube and can lead to its destruction.